sort sorts a list of coinciding events,
that is all events but the first one have time difference 0.
normalize sorts all coinciding events in a list
thus yielding a canonical representation of a time ordered list.

The next set of routines is more precise.
It computes a time table starting with current system time
and tries to stick to it.

So far, I worked hard to use time differences instead of absolute times
in order to avoid increasing memory consumption of time numbers
(which however slows down as time evolves)
but the time related functions of the system are absolute,
so have to make our ones absolute as well.